Bloomfield is located on part of Rancho Cañada de Pogolimi.

In 1853, William Zellhardt built a house on the site of present-day Bloomfield, which attracted other immigrants and led to plans for a town in 1856.

At one point in the late 1850s, Bloomfield was the second largest town in Sonoma County, and in 1877 it had four hotels and a population of 250.

[3] According to the United States Census Bureau, the CDP covers an area of 8.1 square miles (21.1 km2), 99.92% of it land and 0.08% of it water.

There were 143 housing units at an average density of 17.6 per square mile (6.8/km2), of which 65.9% were owner-occupied and 34.1% were occupied by renters.